One particular application of the invention relates to an accessory which can be used with drill rigs which are to be used in drilling bore holes. Such drill rigs generally comprise an upstanding mast which has a drill head mounted to it where the drill head is capable of movement along the mast and the drill head is provided with means which can receive and engage the upper end of a drill string and can apply a rotational force to the drill string to cause it to rotate within the bore hole whereby such rotation results in the cutting action by the drill bit mounted to the lower end of the drill string. The drill string comprises a number of lengths of drill rod which are connected end to end and where the length of drill rod generally is at the most equal to the height of the mast. It is usual that each length of the length of drill rod can be up to a length of the order of six meters. During a drilling operation when the drill head has reached the lower end of the mast, the drill string is clampingly retained and the drill head is disconnected from the drill string. A fresh length of drill rod is then raised into position in order that the upper end of the fresh length is engaged to the drill head and the lower end of the fresh length is engaged with the upper end of the drill string. Once the fresh length of drill rod has been installed, the drilling operation can recommence until the drill head again reaches the lower end of the mast. During drilling activities of deep bore holes which may extend for hundreds of meters, it is necessary to locate fresh lengths of drill rod into a drill string at very regular intervals.
It is usual that the drill rig is mounted to the chassis of a motorised vehicle such as a truck or lorry and that the lengths of drill rod are mounted in a storage zone such that they lie horizontally in a stacked array beside the drilling mast on the same vehicle or alternatively on a vehicle parked alongside the drilling rig or on the ground beside the drilling rig.
The usual method for raising a fresh length of drill rod from the bin to the mast comprises mounting a holder along the length of the length of drill rod connecting that holder to a cable carried by a winch located at the upper end of the mast and then lifting the length of drill rod into position. This requires manipulation by a member of the drill rig crew who is required to support and guide the lowermost end of the length of drill rod as the length of drill rod is being raised into position. Due to the nature of drilling sites, this action can be quite hazardous. In addition, during the raising of the drilling drill rod, it has been known for the upper portion of the length of drill rod to strike some obstruction on the drill mast which causes the lower end to move in an unpredictable manner which can result in injury to the crew member. In addition, this process requires joint coordination between the crew member guiding the one end and the other crew member controlling the winch.
Similarly during the raising of a drill string, it becomes necessary to regularly remove lengths of drill rod from a drill string and locate those lengths in the storage zone located beside the mast which may be either located on the same vehicle as the drilling rig or oh some adjacent vehicle or on the ground beside the drilling rig. This can also create hazards for the personnel required to handle and store the lengths of drill rod.
In the past alternative arrangements have been proposed for the handling of drill rods and examples of such are described in AU693382 and U.S. Pat. No. 6,298,927.
The discussion throughout this specification, of the background and prior art to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia or the world as at the priority date of the application.
It is an object of this invention to provide a means of supporting and handling elongate item such as lengths of drill rod between the storage area for those items and the erect position which can reduce the likelihood of injury to personnel.
It is also an object of the invention to improve the efficiency of drill rod handling.